1. Field of the Invention
The present invention relates to a camera module with double barrels, and more particularly to a camera module with double barrels which can eliminate a problem in that part of an image is cut off when adjusting the focus of a camera for a vehicle which uses a specific lens called an anamorphic lens which is asymmetric with respect to an axis.
2. Description of the Related Art
Generally, a lens used in a camera module is symmetric with respect to a central axis and focusing of the lens is performed by rotating a screw provided to a body of a lens barrel. When using the general lens of which the shape is symmetric with respect to a central axis, image loss does not occur because rotation does not occur.
However, when adjusting the focus of a camera using the anamorphic lens which is developed to obtain an image with no distortion, rotation occurs and therefore part of the image is cut off because the anamorphic lens is asymmetric.
FIG. 5 shows a known camera module. Focusing of the lens of the camera using a general lens is performed by rotating a screw provided to a body of a lens barrel. Since the general lens has a symmetric shape, rotation does not occur and the image loss does not occur. On the other hand, since the camera module for a vehicle uses a specific lens called anamorphic lens to obtain a less-distorted image, it is difficult to precisely focus the lens because the lens shape is asymmetric and therefore the rotation and image loss occur when the focusing is performed by rotating the screw of the lens barrel.
The known camera module shown in FIG. 5 includes a lens barrel 10 in which a plurality of lenses is embedded, a housing 20 which is rectangular parallelopiped and encases and protects the lens barrel 10, an image sensor 30, and a circuit board 40 combined with the image sensor 30.
The inside of the lens barrel 10 is provided with a plurality of general lenses 11. Since the general lens 11 is symmetric with respect to a central axis thereof, the rotation does not occur when focusing the lenses by rotating the lens barrel 10 and therefore the image loss also does not occur. Accordingly, it is easy to focus the lens by rotating the screw of the lens barrel 10.
The housing 20 encases and protects the lens barrel 10 and is coupled to the circuit board 40 to also protect the image sensor 30. A portion of the inside surface of the housing 20 which is to be coupled to the lens barrel 10 is provided with screw grooves which engage with screw threads of the lens barrel 10. The housing 20 has a box shape.
The image sensor 30 is a device for converting an image of an object projected through the lens barrel to an electrical signal, is installed at a center portion of the circuit board 40, and is electrically connected to one edge of the circuit board 40 through a wire-bonding method.
The circuit board 40 is a unit for transmitting the electrical signal generated by the image sensor 30 to a vehicle-specific camera module or a camera phone and an upper surface of the circuit board 40 is provided with the image sensor 30 and circuits to which various passive elements are electrically connected.
In conclusion, the known camera module has the general lens 11 which is symmetric with respect to the central axis thereof. Accordingly, focusing of the lens of the camera is performed by rotating the screw of the lens barrel. Since the lens is a symmetric lens, the rotation does not occur and therefore the image loss does not occur.
On the other hand, as for the vehicle-specific camera module, the specific lens called Anamorphic is used to reduce distortion of the image. Since the specific lens is asymmetric with respect to the central axis thereof, rotation occurs, resulting in image loss in the case of focusing the lens according to the known focus adjusting method. In order to solve this problem, various efforts have been made. That is, when focusing the lens of a camera module with a single barrel, a plate having a predetermined thickness is provided between the barrel and a film or the barrel and an image surface of an imaging element, or a screw or a cam is used to focus the lens of the camera.
Such a focusing manner is effective for focusing a center portion of the lens but resolution of up, down, left, and right side portions of the lens fluctuate according to processing and assembly errors.
Accordingly, a user must dissemble, rotate, and reassemble the barrel or replace the lens group with another one, and then test the lens of the camera to obtain allowable resolution of the peripheral portions of the lens. It is troublesome and takes a lot of labor and time, resulting in a decrease in productivity.
Accordingly, improvement of a barrel structure and a focusing method of a camera which effectively focus the anamorphic lens has been long longed for.